Continuous Vocalization during Kendo Exercises Suppresses Expiration of CO2

One distinctive trait of kendo, the Japanese martial art of fencing, is the execution of sustained, high-effort vocalizations during actions. The purpose of this study was to determine the effect of these vocalizations on respiratory functions. First, the intensity of 3 kendo exercises was quantified by measuring oxygen uptake (V̇O2) and comparing it with V̇O2max measured during treadmill tests of 8 university kendo athletes. Respiratory variables of these 8 athletes were then analyzed using a portable breath gas analyzer during the most intensive kendo exercise, kakari-keiko, with and without vocalization. Breathing frequency (fB) increased regardless of vocalization, but in trials with vocalization, fB and ventilation were significantly lower, and expiration time was significantly longer. Components of expired gases were also affected by vocalization. Although there was no significant difference in oxygen uptake, vocalization yielded a reduction in carbon dioxide output (V̇CO2) and an increase in fraction of end-tidal carbon dioxide (FetCO2). We thus conclude that these vocalizations greatly affect expiration breathing patterns in kendo. Moreover, repetition of kakari-keiko caused a reduction in V̇CO2 and an increase in FetCO2 and CO2 storage. We consider the possibility that the sustained high-effort vocalizations of kendo also increase cerebral blood flow.